DESCRIPTION: The goals of this study are to better understand the mechanism of retroviral DNA integration into the host genome and to evaluate its potential for the practical application in gene therapy. The specific aims are 1) to determine the role of ASV integrase (IN) in the nuclear entry and DNA targeting of the ASV preintegration complex focussing on the nuclear localization signal (NLS) and its potential interacting cellular proteins; and 2) to determine if DNA integration can be targeted to specific sites in host cell chromatin using ASV IN fusion protein.